This study was designed to assess i) the reproducibility of dithiocarbamate excretion by the same individual after repeated doses of broccoli sprout isothiocyanates; and ii) the relationship of dithiocarbamate excretion in urine to escalating doses of broccoli sprout isothiocyanates. Four healthy volunteers were admitted to a 20 day inpatient study. During the entire study, a diet devoid of glucosinolates and isothiocyanates was provided, and urine for dithiocarbamate determination was continuously collected. After a baseline period, each subject was given a 100 mmol dose of sprout isothiocyanates every 48 hr, then a dose of 50, 200, or 400 mmol every 72 h. Three subjects completed the study. Urinary excretion over 48h after repeated doses of 100 mmol was remarkably reproducible at 55.1 1 1.8 mmol (M 1 SD), and excretion was linearly related to dose (R2 = 0.997). These findings suggest the metabolic pathway for isothiocyanate disposition are not saturated at the doses studied.